Knee braces and hinge systems are commonly externally affixed to the lower extremity to stabilize the injured, unstable, and painful knee. Traditional application of knee orthotic hinges, joints, and devices have encountered established problems. In an attempt to stabilize the human knee and match the complex motion it presents, prior designs have compromised functional usage in regard to athletics and activities of daily living.
To provide support and stability the device must transmit certain mechanical forces that counteract and balance the abnormal forces present which are initiating the instability and that result in pain and deformity. The mechanical principles that correct the deformity and prevent injury/re-injury have long been identified and are well understood. It is the transmission of these correcting and stabilizing forces to the human tissue at tolerable levels that remains unsolved by prior art.
In addition, prior art has attempted to resolve the long standing problem of providing stability to the injured and unstable knee while at the same time avoiding rotation and loss of suspension of the device with resultant skin abrasions and abnormal stresses to the knee due to the inability of the device to match normal kinematics of the human knee. Current designs such as the Genucentric Knee Hinge and the Northwestern Knee Orthosis (U.S. Pat. No. 4,361,142) have established claim to resolution of these problems.
Existing devices suffer the disadvantages of excessive bulk, weight, and the inability to match the functional anthropometric contours of the human extremity. Many also fail to apply necessary corrective and supportive total contact forces. Total or full contact forces are required to bring corrective pressures within reasonable, tolerable levels. It is known that Pressure=Force/Area (P=F/A). The greater the area over which a force is distributed, the less the pressure resulting from a given force. Body weight and activity forces are of a large magnitude but nevertheless pressure must be applied at tolerable levels.
Because these problems remain unresolved in the prior art, many devices are subjected to a high rate of user/wearer rejection.
Often, bilateral involvement (that is, of both knees) occurs. With prior art, the protruding bulk of the componentry impedes normal bipedal activity and functional efficient gait is impaired. The resultant poor cosmesis of the devices adds to the high user/wearer rejection rate. Bilateral involvement requires a low profile design which does not significantly increase the girth and circumference dimensions of the device.
Another failing of many prior art devices is the failure to restrict extension of the lower leg at the knee joint. Current orthopedic surgical management mandates limited excursion of extension or approximately 10.degree. to 20.degree. of terminal extension to protect surgical reconstruction. This corresponds to 170.degree.-160.degree. of extension of the knee joint.